The amphibious assault ship USS Bataan returned to open waters Friday after undergoing much-needed maintenance after its near-record 135 days at sea in an area of heightened tension, which put a strain on the amphibious ready group and the ship’s crew.

Aircraft carriers are perhaps the most powerful expression of U.S. military might. They’re also expensive and potentially vulnerable. In an era of fiscal constraint, defense officials, lawmakers and the commander in chief must answer a question that could have enormous strategic consequences: How many are enough?

It also calls for a single “cybersafe” authority to protect the service’s networks.

The plan, which is tied to the Navy’s 2015-2019 spending submission, would continue the Obama administration’s rebalance to the Pacific by expanding the number of ships in the region to 65 in 2019, an increase of 15 ships from this year, Chief of Naval Operations Adm. Jonathan Greenert wrote in the four-page plan.

The Navy’s “most capable platforms will operate in the Western Pacific,” including the newest DDG class of guided missile destroyers, joint high speed vessels, Poseidon surveillance planes, Growler fighter jets and other upgraded aircraft, such as the F-35C Joint Strike Fighter.

An additional attack submarine will join three already in Guam in 2015.

Rear Adm. William Lescher, the deputy assistant secretary of the Navy for budget, told reporters in March that the service was cutting expenses by halving the number of F-35Cs it would buy during the next five years from 69 to 36.

The Navy has requested $125.2 billion for fiscal year 2015, about $400 million less than this year’s enacted budget.

“Despite likely sequestration in 2016, our priority is to operate forward where it matters, when it matters, and be ready to address a wide range of threats and contingencies,” Greenert wrote.

The plan, however, made no reference to the Navy’s goal of assembling a 306-ship fleet by 2020, as it projected in a 30-year plan submitted to Congress in July. Nor did it broach the subject of whether the service will maintain its number of aircraft carriers at 11.

Defense Secretary Chuck Hagel has recommended the carrier USS George Washington be retired in 2016, a move that Greenert has said he opposes.

The plan would increase ships in the Middle East from the current 30 to about 40 in 2019. The 10 patrol craft that now operate out of Bahrain will be joined by four littoral combat ships by the end of 2019.

A “low-cost and small footprint” naval presence is planned for the continents of Africa and South America, Greenert wrote. Beginning in 2015, the Navy will deploy one hospital ship a year to South America, followed by one coastal patrol ship each year beginning in 2016.

The plan did not specify deployments to Africa.

Greenert calls on the Navy to sustain “our advantage in the undersea domain” as it adds the 12th Virginia-class attack submarine to the fleet in 2015, with eight more expected to join by 2019.

An unspecified number of guided missile cruisers and dock landing ships will be modernized to extend their service lives, which Greenert conceded was not his “first choice,” but “budget limits compel us to take this course.”

To beef up cybersecurity, the Navy is establishing a single “cybersafe” authority to manage the service’s networks, platforms and systems “cradle to grave,” the plan stated.

“We are also proceeding to recruit, train and hire almost 1,000 cyber operators and are on track to form 40 cyber mission teams by the end of 2016,” Greenert wrote.

Greenert is expected to release a position report later in this year that reviews the Navy's progress in implementing the objectives of previous navigation plans.